====== SED - Delete - Delete all CONSECUTIVE blank lines from file except the first ======

Also deletes all blank lines from top and end of file (emulates "cat -s").

<code bash>
sed '/./,/^$/!d'          # method 1, allows 0 blanks at top, 1 at EOF
sed '/^$/N;/\n$/D'        # method 2, allows 1 blank at top, 0 at EOF
</code>